The disclosure of Japanese Patent Application No. 2000-400983 filed on Dec. 28, 2000 including the specification, drawings and abstract is incorporated herein by reference in its entirety.
1. Field of the Invention
The present invention relates generally to an active vibration damping device usable for vibration dampers devices for automotive vehicles, such as an engine mount and a body mount, and capable of actively exhibiting a vibration damping effect or actively offsetting vibrations to be damped. More particularly, the present invention is concerned with a fluid-filled active vibration damping device that includes a pressure receiving chamber partially defined by an oscillating member and filled with a non compressible fluid, and an actuator adapted to oscillate the oscillating member for regulating the pressure of the non-compressible fluid in the pressure-receiving chamber so that the vibration damping device actively exhibits a desired vibration damping effect.
2. Description of the Related Art
A fluid-filed active vibration damping device is known as one type of vibration damping devices, e.g., a vibration damping mount or a vibration damping bushing, which is interposed between two members of vibration system for elastically connecting two members in a vibration damping fashion. As disclosed in JP-A-2-42228, JP-A-10-47426 and JP-A-11-247919, a known example of such a fluid-filled active vibration damping device includes a first and a second mounting member, an elastic body elastically connecting the first and the second mounting members, and partially defining a fluid chamber filled with a non-compressible fluid and adapted to receive a vibration load, an oscillating member partially defining the fluid chamber, and an electromagnetic actuator adapted to oscillate the oscillating member in order to regulate a pressure of the non-compressible fluid in the fluid chamber. The known fluid-filled active vibration damping device is adapted to apply oscillating force corresponding to vibrations to be damped between two members of the vibration system, so as to offset or absorb the vibrations to be damped, or so as to actively change spring characteristics of the vibration damping device corresponding to an input vibration so that the vibration damping device exhibits a low dynamic spring constant with respect to the input vibration. Thus, the fluid-filled active vibration-damping device is capable of exhibiting active vibration damping effects with respect to vibrations to be damped. For the above reasons, the fluid-filled active vibration-damping device has been applied to the engine mount for the automotive vehicles, for example.
In order to ensure a desired vibration damping effect of such a fluid-filled active vibration damping device, it is needed to oscillate the oscillating member at a frequency and a phase that correspond to those of the vibrations to be damped with high accuracy. To meet this requirement, the actuator may be preferably selected from an electromagnetic actuator, a voice-coil type actuator or the like. In general, the actuator may be formed independently of an mounting assembly of the vibration damping device, i.e., an intermediate assembly including the first and second mounting members, the elastic body elastically connecting the first and second mounting members, and the pressure-receiving chamber partially defined by the elastic body. This independently formed actuator is fixedly connected at its power output shaft to the oscillating member of the mounting assembly of the vibration-damping device
In the conventional fluid-filled active vibration damping device as described in the above-indicated documents, the power output shaft of the actuator is fixed to the oscillating member such that the power output shaft is screwed onto a fixing bolt fixed to the oscillating member and extending coaxially with the power output shaft. However, this conventional mechanism for fixing the power output shaft to the oscillating member needs cumbersome and time-consuming operation or processes. Moreover, a reaction force of a twisting force generated upon screwing the power output shaft of the actuator to the fixing bolt fixed to the oscillating member acts on the oscillating member, possibly causing undesirable damage of the oscillating member.
Further, JP-A-6-264955 and JP-A-11-351313 disclose another type of conventional fluid-filled active vibration damping device, in which the oscillating member has a drive shaft fixedly disposed thereon so as to protrudes toward the actuator. The drive shaft of the oscillating member and the power output shaft of the actuator are superposed on each other in a radial direction perpendicular to their axial direction, and fastened together by means of a suitable fastening means, e.g., a bolt and a rivet, which extends through the drive shaft and the power output shaft in the radial direction. In this arrangement, the oscillating member is free from a problem that the oscillating member is undesirably damaged due to reaction force acting thereon upon fixing the drive shaft and the power output shaft together.
However, the conventional fluid-filled active vibration damping device disclosed in JP-A-6-264955 and JP-A-11-351313 suffers from a difficulty in providing a space enough large for executing a required operation for fastening the mutually superposed power output shaft and the drive shaft together by the bolt or rivet extending therethrough. Therefore, the conventional fluid-filled active vibration-damping device still has room for improving in terms of efficiency of manufacturing of the vibration-damping device.
In addition, the actuator used in the conventional fluid-filled active vibration damping device includes a coil to be energized which is fixed to an outer circumferential portion thereof, and an attractive member such as a permanent magnet and a magnetic member disposed within a bore of the coil. In this arrangement, an entire length of a wire winding around the coil is inevitably made long, for ensuring the sufficiently large number of winding of the coil, resulting in a high tendency toward increase of electrical resistance. As a result, the actuator suffers from deterioration of electrical efficiency thereof, so that the actuator becomes incapable of generating a desired oscillating force with high efficiency.
It is therefore one object of this invention to provide a fluid-filled active vibration damping device which is novel in construction and which makes it possible to assemble a mounting assembly of the vibration-damping device and an actuator formed independently of the mounting assembly to each other with excellent operation efficiency, and a method of producing the same.
It is another object of this invention to provide a fluid-filled active vibration damping device which is novel in construction and which is capable of efficiently generating a relatively large oscillating force with a reduced electric current applied to a coil, and a method of producing the same.
The above and/or optional objects of this invention may be attained according to at least one of the following modes of the invention. Each of these modes of the invention is numbered like the appended claims and depends from the other mode or modes, where appropriate, to indicate possible combinations of elements or technical features of the invention. It is to be understood that the principle of the invention is not limited to those modes of the invention and combinations of the technical features, but may otherwise be recognized based on the thought of the present invention that disclosed in the whose specification and drawings or that may be recognized by those skilled in the art in the light of the disclosure in the whole specification and drawings.
(1) A fluid-filled active vibration damping device comprising: (a) a first and a second mounting member which are spaced apart from each other; (b) an elastic body elastically connecting the first and second mounting members and partially defining a fluid chamber filled with a non-compressible fluid; (c) an oscillating member partially defining the pressure-receiving chamber on one of opposite sides thereof; (d) an electromagnetic actuator disposed on an other one of the opposite sides of the oscillating member and adapted to oscillate the oscillating member so as to control a pressure of the non-compressible fluid in the fluid chamber, the electromagnetic actuator includes: a coil having a bore; a yoke member made of a magnetic material and disposed in the bore of the coil so as to extend through the bore and protrudes axially outwardly from axially opposite end faces of the coil so as to form circumferentially extending magnetic pole portions on axially opposite sides of the coil; an oscillating sleeve member made of a magnetic material that is disposed radially outwardly of the yoke member with a given radial spacing therebetween such that the yoke member and the oscillating sleeve member are displaceable relative to each other in an axial direction of the electromagnetic actuator, the oscillating sleeve member being adapted to form at least one annular attractive portion; and an elastic support member for elastically positioning the oscillating sleeve member and the yoke member relative to each other in the axial direction, such that the at least one annular attractive portion of the oscillating member is opposed to at least one of the magnetic pole portions in a radial direction perpendicular to the axial direction, and is offset from each other in the axial direction, when the coil is in a non-energized state, the coil being energized in order to apply an axial driving force between the yoke member and the oscillating sleeve member on the basis of a magnetic force acting between the magnetic pole portions and the annular attractive portion mutually opposed to each other in the radial direction and offset from each other in the axial direction, and (g) a cup-shaped retainer fixed to the second mounting member and adapted to accommodate the electromagnetic actuator such that the electromagnetic actuator extends in a direction in which the oscillating member is reciprocatory oscillated, the annular attractive portion is fixedly connected to the oscillating member on one of axially opposite sides of the electromagnetic actuator, and the yoke member is fixedly connected to a bottom wall portion of the retainer on an other one of the axially opposite side of the electromagnetic actuator such that the yoke member extends through the bottom wall portion of the retainer.
In the fluid-filled active vibration damping device according to this mode (1) of the invention, the electromagnetic actuator can be fixedly assembled with the second mounting member via the retainer by effectively utilizing the yoke member thereof. Namely, the electromagnetic actuator is fixedly connected to the second mounting member by means of the retainer that is fixed to the inner yoke of the electromagnetic actuator extending through the bottom wall portion thereof. This makes it possible to fix the yoke member to the second mounting member via the retainer, after the annular attractive portion is connected to the oscillating member. In other words, the operation for connecting the annular attractive portion and the oscillating member is executed before the retainer covers the electromagnetic actuator and the oscillating member. Therefore, this arrangement permits both of a simple construction of the fluid-filled active vibration damping device and an improved efficiency for manufacturing the fluid-filled active vibration damping device.
In the electromagnetic actuator of the fluid-filled active vibration damping device of this mode (1) of the invention, the yoke member assembled with the coil is disposed in the radially inner side of the actuator (i.e., in the vicinity of an axis of the actuator) and the oscillating member is disposed in the radially outer side of the actuator. In this arrangement, a total length of a wire winding around the coil is made smaller than that in the above-described conventional actuator where the coil is disposed in the radially outer side of the actuator, even if the number of the winding of these coils are made equal. In other words, the total length of the wire winding around the coil is made small to the number of winding of the coil. The electromagnetic actuator used in the vibration-damping device of this mode exhibits a low electric resistance of the coil, so that the electromagnetic actuator can generate magnetic force with high efficiency, upon energizing the coil. As a result, the electromagnetic actuator generates an axial oscillating force with high efficiency, thereby effectively assuring a desired oscillating force generated by the oscillation of the oscillating member.
In addition, the electromagnetic actuator used in the fluid-filled active vibration damping device of this mode, makes it possible to provide magnetic force acting portions, i.e., the magnetic pole portions and the annular attractive portion at a radially outer portion thereof. This arrangement is effective to increase a circumferential length and a resultant total area of the magnetic pole portions and the annular attractive portion, in comparison with the above-described conventional actuator in which the coil is disposed in the radially outer portion of the actuator, even if the electromagnetic actuator used in the present invention and the conventional actuator have the same overall size. Thus, the electromagnetic actuator is able to generate the axial driving force with high efficiency, whereby the fluid-filled active vibration damping device can be generate the desired oscillating force with high efficiency.
Various kinds of fixing devices or mechanisms may be employed for fixing the electromagnetic actuator to the retainer. For instance, the electromagnetic actuator and the retainer may be fixed by bolting, press fitting, calking or the like. Preferably, the electromagnetic actuator and the retainer may be fixed together by means of a fastening mechanism. Described in detail, one of axially opposite end portions of the yoke member located on the side of the bottom wall portion of the retainer, protrudes axially outwardly through the bottom wall of the retainer. An external thread is formed on the outer circumferential surface of the protruding end portion of the yoke member, to thereby form a bolt portion. A fixing nut is screwed into the bolt portion of the yoke member, thereby fastening the electromagnetic actuator and the retainer together.
(2) A fluid-filled active vibration damping device according to the above-indicated mode (1) wherein the electromagnetic actuator further includes a power output shaft that protrudes on a center axis of the vibration damping device from the annular attractive portion toward the oscillating member, and the oscillating member further includes a drive shaft that protrudes on the center axis of the vibration damping device from the oscillating member toward the electromagnetic actuator, the drive shaft and the power output shaft being superposed on each other in a direction perpendicular to the center axis of the vibration damping device and fastened together by means of an engaging shaft member extending therethrough, whereby the oscillating member and the annular attracting portion of the electromagnetic actuator are fixedly connected to each other. According to this mode (2) of the invention, the vibration-damping device is free from a problem of axial displacement of the drive shaft and the power output shaft relative to each other, while making it possible to fixedly connect the drive shaft and the power output shaft together with ease and with a simple structure. The engaging shaft member may be selected from a rivet, a bolt, a pin a fixing rod or other suitable fastening members.
(3) A fluid-filled active vibration damping device according to the above-indicated mode (1) or (2), wherein the elastic support member comprises a pair of metallic leaf springs each having a disk like shape, which are disposed on axially opposite sides of the electromagnetic actuator so as to extend in a radial direction perpendicular to an axial direction of the electromagnetic actuator between the yoke member and the oscillating sleeve member, each of the pair of metallic leaf springs being fixed at an inner peripheral portion thereof to the yoke member and at an outer peripheral portion thereof to the oscillating sleeve member. In this mode (3) of the invention, the pair of leaf springs function to allow an axial displacement of the oscillating sleeve member relative to the yoke member, while preventing or restricting a displacement of the oscillating sleeve member relative to the yoke member in a direction in which the oscillating sleeve member is eccentric or inclined to the yoke member. Thus, the presence of the pair of leaf spring enables to improve an operation stability of the electromagnetic actuator. Preferably, each of the metallic leaf springs is formed with a through hole having a desired configuration, to thereby adjust elasticity thereof in the axial direction. For instance, the each metallic leaf spring has a plurality of through holes so as to form a plurality of elastic connecting portion that cooperate to spirally extend from its outer peripheral portion to its central portion.
(4) A fluid-filled active vibration damping device according to any one of the above-indicated modes (1)-(3), wherein the yoke member includes a bore open in an end face of one of axially opposite end portions thereof that extends through and fixed to the bottom wall portion of the retainer, the bore being adapted to accommodate a lead wire connected to the coil for applying an electric current to the coil. This arrangement enables to take the lead wire connected to the coil out of the retainer with ease, and without needing an additional arrangement with respect to the retainer for taking the lead wire out of the retainer.
(5) A fluid-filled active vibration damping device according to the above-indicated mode (4), wherein the oscillating sleeve member further includes an upper wall portion disposed at one of axially opposite open end portions thereof that is located on the side of the oscillating member, the power output shaft being fixedly disposed on a central portion of the upper wall portion so as to protrude toward the oscillating member, and wherein the bore of the inner yoke member extends over an entire axial length of the inner yoke member and is opposed at one of axially opposite ends thereof located on the side of the oscillating member to the upper wall portion of the oscillating sleeve member, the one of axially opposite ends of the bore of the inner yoke member being provided with a buffing member fixed thereto. In this mode (5) of the invention, the power output shaft can be disposed on an center axis of the oscillating sleeve member so as to protrude toward the oscillating member. This makes it possible to transmit the drive force generated in the electromagnetic actuator to the oscillating member with high efficiency with a simple connecting structure. Moreover, the power output shaft formed on one of opposite sides of the upper wall portion of the oscillating sleeve member is axially opposed to the buffing member fixed to the one end of the inner yoke member located on the other side of the upper wall portion with a given axial spacing. In this arrangement, the upper wall portion of the oscillating sleeve member is brought into abutting contact with the one end of inner yoke member via the buffing member in a shock-absorbing fashion, to thereby constitute a stop mechanism for limiting an amount of displacement of the oscillating member toward the electromagnetic actuator. Namely, the stop mechanism can be advantageously realized with a simple structure by effectively utilizing the bore of the yoke member.
(6) A fluid-filled active vibration damping device according to the above-indicated modes (1)-(5), wherein the second mounting member includes a cylindrical portion, one of axially opposite open ends of the cylindrical portion being opposed to the first mounting member with a spacing therebetween and being fluid-tightly closed by the elastic body elastically connecting the first and second mounting member together, and an other one of the axially opposite open ends of the cylindrical portion being fluid-tightly closed by a flexible diaphragm which is easily deformable, the oscillating member being axially movably supported by an axially intermediate portion of the cylindrical portion of the second mounting member such that the pressure receiving chamber partially defined by the elastic body is formed on one of axially opposite sides of the oscillating member and an equilibrium chamber partially defined by the flexible diaphragm is formed on an other one of axially opposite sides of the oscillating member, the fluid-filled active vibration damping device further comprising an orifice passage for fluid communication between the pressure receiving chamber and the equilibrium chamber and a connecting member fluid-tightly fixed to and extending through the flexible diaphragm, and wherein the electromagnetic actuator is disposed on one of opposite sides of the flexible diaphragm remote from the equilibrium chamber, and the retainer supporting the electromagnetic actuator is fixed at an open end portion thereof to the other one of the axially opposite open end of the cylindrical portion of the second mounting member, while the connecting member is fixed at one of opposite end portions thereof protruding toward the equilibrium chamber to the oscillating member and at an other one of opposite end portions protruding toward the electromagnetic actuator to the oscillating sleeve member of the electromagnetic actuator.
According to this mode (6) of the invention, the fluid-filled active vibration damping device is capable of effectively adjusting or controlling a pressure change of the fluid in the pressure receiving chamber upon application of a vibrational load to the device passively and/or actively, by utilizing resonance of the fluid flowing through the orifice passage on the basis of the pressure difference between the pressure receiving chamber and the equilibrium chamber. Thus, the fluid-filled active vibration-damping device of this mode (6) can exhibit a further improved vibration damping capability. In addition, the connecting member fluid-tightly extending through the flexible diaphragm is utilized for connecting the oscillating member and the electromagnetic actuator that are disposed on the opposite sides of the equilibrium chamber. This arrangement is effective to realize an oscillating mechanism for oscillating the oscillating member by utilizing the electromagnetic actuator, while assuring excellent fluid-tight sealing of the equilibrium chamber.
In the fluid-filled active vibration damping device of the above-mode (6), the presence of the connecting member ensures that the output shaft of the electromagnetic actuator and the oscillating member are firmly and fixedly connected to each other, even if the equilibrium chamber interposed between the oscillating member and the power output shaft of the electromagnetic actuator. Namely, the drive force generated by the electromagnetic actuator is directly transmitted to the oscillating member via the rigid connecting member, not via the flexible diaphragm and the fluid. Thus, the fluid-filled active vibration damping device permits an improved power transmitting efficiency between the electromagnetic actuator and the oscillating member and a resultant improved accuracy of control of the oscillation of the oscillating member.
In the fluid-filled active vibration damping device of the mode (6), the oscillating member and the connecting member are formed independently of each other. This makes it possible to form the an oscillating rubber support adapted to elastically support the oscillating member to the cylindrical portion of the second mounting member independently of the flexible diaphragm integrally bonded to the connecting member in the process of vulcanization of a rubber material for forming the flexible diaphragm. For the above reason, the oscillating rubber support and the flexible diaphragm can be independently arranged with a high degree of freedom in selecting materials, configurations, and other properties.
(7) A method of producing a fluid-filled active vibration damping device constructed according to any one of the above-indicated modes (1)-(7), wherein the first and second mounting member and the elastic body and the fluid chamber cooperate to form a mounting assembly of the vibration damping device, the method comprising the steps of: preparing the mounting assembly and the electromagnetic actuator independently of each other; fixedly connecting the oscillating sleeve member of the electromagnetic actuator to the oscillating member of the mounting assembly; assembling the retainer with respect to the electromagnetic actuator such that the retainer is disposed radially outwardly of the electromagnetic actuator; and then fixing the retainer to a fixing member of the second mounting member and the yoke member of the electromagnetic actuator to the bottom-wall portion of the retainer such that the yoke member extends through the bottom wall portion of the retainer.
According to the method of producing the fluid-filled active vibration damping device of this invention, the oscillating sleeve member of the independently formed electromagnetic actuator is fixedly connected to the oscillating member of the mounting assembly, initially. Subsequently the retainer is fixed to the mounting assembly, while the yoke member of the electromagnetic actuator is fixed to the retainer. That is, the electromagnetic actuator can be supported by the mounting assembly via the retainer. It should be appreciated that the present method makes it possible to easily perform an operation for fixedly connecting the oscillating sleeve member of the electromagnetic actuator to the oscillating member of the mounting assembly, before the retainer covers the electromagnetic actuator and the oscillating member. Therefore, the present method makes it possible to form a desired fluid-filled active vibration-damping device with ease and with excellent efficiency for manufacture. In the present mode (7) of the invention, the mounting assembly should be interpreted to mean an intermediate assembly of the fluid-filled active vibration damping device, which does not includes the electromagnetic actuator and the retainer, and which includes the fluid chamber filled with the non-compressible fluid whose pressure varies upon application of a vibrational load to the intermediate assembly.